Shade cloth density refers to how much sunlight a shade cloth blocks. The higher the percentage, the more sunlight being blocked. So, a shade cloth with 10% density is only blocking 10% of sunlight, while a shade cloth with 90% density is blocking 90% of the sunlight.The main point of shade cloth is to provide shade, so the shade cloth density--the amount of sunlight being blocked--is really the key feature to consider.
The percentage of the shade cloth corresponds to the amount of light which is blocked by this cloth. The shade clothes typically come in 30%, 55%, 63%, 75%, 80% and 90% options.
This is due to the structure of the cloth. If a hole forms in the knitted shade cloth the threads running in different directions will not unravel.
Moreover, knitted option is resistant to the most of the horticultural chemicals and detergents. The knitted fabric can be stretched up to 3 per cent whilst woven shade cloth can’t.However, there are some plants which require specific shading conditions. For example, orchids and ferns which are shade loving plants require 75% shade cloth to receive the appropriate levels of sunlight.
In general, a 30 to 40 percent cloth is a good rule of thumb for most mixed use greenhouses and varies from there based on your crop, your greenhouse ventilation, your climate, and your greenhouse's orientation to the sun.
For instance, 40 percent shade is recommended for summer greenhouse tomatoes in Michigan, and no shade in winter, while a California grower may use up to an 80 percent cloth in summer and 50 percent in winter.
If your greenhouse is oriented north-south, it will collect less heat in both winter and summer, allowing you to use a less dense shade cloth, or no shade cloth at all. If it is oriented east-west, you will always have sunlight on the broadside of the greenhouse and it will collect more solar heat.
Research has demonstrated that shade cloth can actually increase plant production.